Hypertherm HT4400 HySpeed Plasma Arc Cutting System - Manual (Page 120)

MAINTENANCE
HT4400 Instruction Manual 5-29
3
Start Circuit Board PCB14 - Status Indicators and Operation
See page 6-4 for location of Start Circuit Board.
Operation
The start circuit is a high-speed switch that quickly transfers the pilot arc current from the pilot arc load to the
work load. The start circuit performs 2 functions:
1. It allows the initial pilot arc current to flow through the pilot arc lead quickly, with little impedance.
2. After initial pilot arc current is established, the start circuit introduces impedance to the pilot arc load to
aid in transferring the arc current to the workpiece. See schematic on following page.
Pilot Arc Current Levels
The pilot arc current level will change depending on the chosen process and arc current level. See table below.
O2 as the Plasma Gas Pilot Arc Current
100-amp current setting 30 amps
200-amp current setting 44 amps
300-amp and 400-amp current setting 60 amps
N2 as the Plasma Gas Pilot Arc Current
200-amp current setting 44 amps
400-amp current setting 60 amps
D2
+15 VDC D1
IGBT Output
J1